The long-term goal of this project is to identify the patterns of age-related change and constancy in the functioning of neural systems that mediate cognitive abilities, especially attention and memory. Recent findings from the present project, based on measures of neural activation obtained from positron emission tomography, suggest that aging is associated with both decreases and increases in regional activation. The proposed research will test healthy, community-dwelling younger and older adults, using event-related functional magnetic resonance imaging (fMRI), to address the following issues: age differences in the shape of the neural hemodynamic response (HDR) waveform, measured from fMRI, in various brain regions (Experiment 1); the role of strategy and memory demands in eliciting age-related increases in prefrontal activation (Experiments 2-3); the relative contributions of top-down and bottom-up attentional processing to age differences in visual search performance (Experiments 4-5); age-related changes in the neural basis of inhibition of response-incompatible information (Experiments 6-7); the differential pattern of prefrontal activation for episodic and semantic memory retrieval processes (Experiment 8); and the neural correlates of age-related declines in episodic encoding and retrieval success (Experiments 9-10). Across all of the experiments, analyses of the temporal characteristics of the HDR functions will be conducted, which will assist the interpretation of age differences within task conditions, as well as the characterization of the relation between neural activation and cognitive performance. The project is designed to provide new information regarding the age-related changes in neural functioning that occur independently of significant disease. The findings will be relevant to the development of functional neuroimaging techniques that can aid in the diagnosis of significant and abnormal cognitive impairment.